An Orbital Sciences Antares rocket carrying a Cygnus cargo capsule thundered away from the Virginia coast Sunday and streaked into orbit, kicking off a three-day flight to deliver more than 1.5 tons of supplies and equipment to the International Space Station.

After a string of delays caused by stormy weather, conflicts with other flights and an engine test failure, the rocket's two Russian-built first stage engines, supplied by Aerojet Rocketdyne, ignited with a roaring rush of fiery exhaust at 12:52 p.m. EDT (GMT-4), generating 734,000 pounds of thrust.

The 133-foot-tall rocket quickly climbed away from pad 0A at the Mid-Atlantic Regional Spaceport at NASA's Wallops Island, Va., flight facility, arcing away to the southeast through a partly cloudy sky and putting on a dramatic Sunday show for area residents and tourists jamming local roads and beaches.

Burning oxygen and RP-1 kerosene rocket fuel, the Aerojet Rocketdyne AJ26 first stage engines fired for nearly four minutes, boosting the rocket out of the dense lower atmosphere and into the orbital plane of the space station.

After a short coast, the rocket's ATK solid-fuel second stage motor ignited at an altitude of about 106 miles and fired for two minutes and 17 seconds or so to put the spacecraft into an initial orbit with a high point, or apogee, of about 185 miles and a low point, or perigee, of around 125 miles.

Two minutes later, the Cygnus cargo ship was released from the second stage to fly on its own. The spacecraft's two solar panels unfolded and locked in place a few moments later, setting the stage for a series of carefully planned rendezvous rocket firings to catch up with the space station.

"We have completed the first burn," said Frank Culbertson, a former shuttle commander who serves as Orbital's vice president and general manager of advanced programs. "We deployed the solar arrays, we're getting full power, and all the systems on the spacecraft are operating nominally. So we're very excited about the fact that we're in orbit and we're headed to the station. ... We're really looking forward to the rendezvous."

If all goes well, the uncrewed Cygnus cargo craft will reach the lab complex early Wednesday, pulling up to within about 30 feet and then standing by while the lab's robot arm, operated by station commander Steve Swanson, locks on to pull it in for berthing at the Earth-facing port of the forward Harmony module.

This is Orbital's second operational station resupply mission under a $1.9 billion contract with NASA that calls for eight flights through 2016 to deliver 20 tons of cargo. SpaceX holds a similar resupply contract, valued at $1.6 billion, for 12 flights to deliver some 44,000 pounds of equipment and supplies.

The commercial contracts were awarded to make up for the lost payload capability of NASA's space shuttle, which was retired in 2011. SpaceX has carried out three operational resupply missions to date with two more flights on tap in September and December and three flights planned next year. Orbital plans its third mission in October with two flights on tap in 2015.

William Gerstenmaier, NASA's director of space operations, said the agency plans to announce a second round of contracts in the December-January timeframe to continue commercial resupply operations past 2016. NASA hopes to operate the space station through 2024, if not longer, and keeping the lab supplied is critical.

An artist's concept of an Orbital Sciences Cygnus cargo ship near the International Space Station. If all goes well, a Cygnus launched Sunday will reach the lab complex early Wednesday. (Credit: NASA)

For the current mission, known as Orb-2, the Cygnus cargo ship was loaded with 3,293 pounds of crew supplies, including food, spare parts and other station hardware, science equipment, spacewalk components and computer hardware.

The research cargo includes a variety of student experiments, supplies for NASA's Human Research Facility lab rack, igniters for the station's combustion test facility and a Japanese experiment designed to study convection in the microgravity environment of space.

Also on board: 28 small satellites -- nanosats -- built by Planet Labs of San Francisco, the third "flock" of spacecraft launched to date for testing in a commercial venture to continuously photograph the Earth. Four other nanosats also are on board, including one built by NASA to test techniques for returning small experiment samples to the ground.

The Cygnus spacecraft will remain attached to the station for about a month. After it is unloaded and re-packed with trash and no-longer-needed equipment, the lab's robot arm will unberth the cargo ship and release it from the station.

Before falling back to Earth and burning up in the atmosphere, the cargo ship will spend a few extra days in orbit for tests of new rendezvous equipment and procedures designed to allow the craft to remain in orbit for extended periods.

NASA originally hoped to launch the Orb-2 mission in May, but the flight was delayed to early June because of conflicts with other launches. Then, on May 22, an Antares first-stage engine being test fired for a flight next year suffered a catastrophic failure. The Orb-2 mission was put on hold pending a failure investigation.

The analysis is not yet complete, but the engines used Sunday were cleared for flight after additional boroscope inspections and a review of earlier test firings. Orbital then scheduled launch for Friday, but the flight slipped to Sunday because of stormy weather that interrupted ground processing.